The overall objective of this project is to gain a better understanding of the biology of pathogenic streptococci in order to control infections caused by these organisms and to prevent their complications (e.g., rheumatic fever and acute nephritis). The studies will emphasize groups A and B stroptococci. Broad objectives will include investigations of: 1) stroptococcal bacteriophages, phage enzymes and phage-associated lysins; 2) the interrelationships and genetics of M protein and other cellular antigens; 3) streptococcal enzymes and antibodies; 4) streptolysin O and the pathogenesis of rheumatic fever; 5) the biology of group B streptococci.